The present invention relates to a method for making a package of products and an apparatus that implements the method.
More specifically, the package is obtained from stretch film and it may contain groups of products such as bottles with bases of different shapesxe2x80x94for example, circular, square or rectangularxe2x80x94or even containers made of metal (including parallelepiped shaped containers).
In conventional production lines where the production process includes the wrapping of groups of plastic bottles (to which the present description will hereinafter refer, although the invention may also be applied to other types of product or container), the final wrapping over the groups of bottles usually consists of a sheet of heat-shrink material.
In some cases and for some types of products, these lines may, however, be very expensive for the manufacturer because they have numerous operating units, such as product collating units (especially in the case of continuous lines), and film feed and heating units, all of which require a high number of control devices and accessory parts. Other negative factors to be taken into account when dealing with production lines of this kind are the high cost of the heat shrink film itself and the fact that some products cannot be heated beyond certain limits, which means that heat shrink wrapping solutions are not feasible.
The teachings of prior art also include more economical wrapping solutions adopted instead of heat shrink wrapping methods and machines, but providing standards of quality that are at least as high as those provided by heat shrink wrapping solutions.
One of these alternative solutions is described in patent IT 1.285.827, to the same Applicant as the present. In this solution, a tubular portion of stretch film, that is to say, elastically extensible film, is used in a method where the portion of film is fed by a film feed station and then stretched transversally by a plurality of rods. In this way, the size of the tubular portion of film is enlarged so that its transversal dimension is increased from a minimum size to a size greater than the front of the groups of products. The rods then align the film with the line of product feed so as to enable a single group of products to move into the stretched tube of film. The rods, moving in synchrony with the feed motion of the groups of products, then release the tube of film allowing it to shrink to its former size in such a way that it envelops the package.
This wrapping method is extremely practical, fast and economical compared to heat shrink wrapping methods and its use is currently preferred for many type of productsxe2x80x94whether bottles or other containersxe2x80x94to be wrapped with film.
In this connection, and in view also of the greatly increased demand for stretch wrapping, there has also been a growing demand for a new type of end package to meet changing consumer requirements and to facilitate handling.
A first solution is disclosed in European patent application No.01830521.9, by the same Applicant as the present, where a stretch film package is made in the following steps: forming groups of products; winding a stretch film unrolled from a first roll around first means for preforming the wrapping, positioned inside a film wrapping area and along the product group line of feed; forming a first tubular portion of stretch film; stretching the portion of film by moving the first preforming means to create an access area for a single group of products moving along the feed line; releasing the portion of stretch film to allow the film to shrink to its former size over the group of products and thus wrapping it; expelling the wrapped package thus obtained onto the feed line.
The step of expelling the package is followed by the further steps of turning the package through ninety degrees and overwrapping it with a second wrap of stretch film unwound from a second roll. In this way, a highly practical and secure double wrapping is placed over the group of products.
With the aim of improving on, and making better use of, the method just described, where the groups of products are wrapped on the same line as that on which they are being fed, the Applicant has devised and produced a variant of it, together with an apparatus to implement it, and a new type of package, which combines security and stability for the products with ease of handling for the package without adding any further elements to the package itself.
The aforementioned aim is accomplished by a method for wrapping groups of products with stretch film comprising the following steps: forming groups of products having a front and a longitudinal dimension that follows a line of feed; placing a first wrapping on the group of products to form a package that holds the products together; expelling the package thus obtained along the feed line; turning the package through an angle of 90xc2x0; placing over the first wrapping a second stretch film wrapping on the package thus obtained, the second wrapping having at least one narrowed strap-like segment surrounding a part of the package.